KR20010021262A - A semiconductor light emitted device and method for manufacturing the same - Google Patents

Abstract

PURPOSE: To surely obtain light emission, having a long wavelength from a green region to a red region by compressing the first layer approximately elastically in the direction parallel with a main surface by the second layer and reducing the difference of a lattice constant with a substrate. CONSTITUTION: A light-emitting device 10A is formed in a constitution, in which an n-GaN buffer layer 12, an MQW layer 13, a p-AlGaN clad layer 14 and a p-GaN layer 15 are laminated successively on an n-GaN substrate 11. When InGaN layers 13a and AlGaN layers 13b in thin-films are laminated, compressive stress in the in-plane direction is applied to the InGaN layers 13a and tensile stress in the in-plane direction is applied to the AlGaN layers 13b respectively. The lattice constants of each layer can be adjusted to values very close to the GaN substrate 11. When the film thickness of each of the InGaN layers 13a and the AlGaN layers 13b is formed into one lower than the so-called 'critical film thickness', elastically deformable one, the generation of crystal defects can be inhibited surely.

Description

Semiconductor light emitting device and method of manufacturing the same {A SEMICONDUCTOR LIGHT EMITTED DEVICE AND METHOD FOR MANUFACTURING THE SAME}

The present invention relates to a semiconductor light emitting device and a method of manufacturing the same.

More particularly, the present invention relates to light emitting devices such as light emitting diodes (LEDs) and laser diodes (LDs) using gallium nitride compound semiconductors, and to a semiconductor light emitting device capable of long wavelength, high brightness and improved reliability. will be.

In addition, the present invention relates to a light emitting device such as a light emitting diode (LED) or a laser diode (LD) made of a gallium nitride compound semiconductor or other materials, and a semiconductor light emitting device having an advantageous formation of a current blocking structure and a method of manufacturing the same. It is about.

In recent years, gallium nitride compound semiconductors have been put into practical use as materials for light emitting devices in a short wavelength region, and light emission such as ultraviolet light, blue, green, etc., which have been difficult until now, has become possible. In addition, the gallium nitride compound semiconductor may have a long emission wavelength of up to 633 nm from the viewpoint of material properties, so that light may be emitted to the red region, and instead of the conventional gallium arsenide (GaAs) system, There is a possibility that light emission can be realized.

In the present invention, as the "gallium nitride compound semiconductor", III- of B _x In _y Al _z Ga _(1-xyz) N (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1) In addition to the group V compound semiconductor, the group V element also contains a mixed crystal containing phosphorus (P), arsenic (As), and the like in addition to N.

8 is a schematic cross-sectional view showing a typical example of a conventional gallium nitride compound semiconductor light emitting device. That is, in the gallium nitride compound semiconductor light emitting device 100, a GaN buffer layer (not shown), an n-type GaN layer 119, an emission layer 120, and a p-type GaN layer 105 are formed on the sapphire substrate 118. It has a laminated structure in this order. A portion of the light emitting layer 120 and the p-type GaN layer 105 is etched away, and the n-type GaN layer 119 is exposed. The p-side transparent electrode 106 and the insulating film 121 for blocking current are provided on the p-type GaN layer 105, and the p-side bonding electrode connected to the p-side transparent electrode 106 on the insulating film 121. 107 is provided. In addition, an n-side electrode 109 is provided on the n-type GaN layer.

In such a structure, the current supplied through the p-side bonding electrode 107 spreads in the in-plane direction to the transparent electrode 106 having good conductivity, and the current flows from the p-type GaN layer 105 to the InGaN light emitting layer 120. The light is injected and emitted, and the light is taken out of the device through the transparent electrode 106.

One characteristic of the conventional light emitting element illustrated in FIG. 8 is that the "lattice ratio matching", that is, the lattice constants of the substrate and the growth layer are significantly different. While the lattice constant of GaN is 3.19 A (Angstrom), the lattice constant of sapphire used as the substrate 118 is 2.75 A, and the lattice mismatch Δa / a reaches 16%. In a conventional gallium nitride compound semiconductor light emitting device, GaN-based crystals containing a large amount of crystal defects are grown on a substrate having greatly different lattice constants to emit light.

By the way, in the material system of a gallium nitride compound semiconductor as shown in FIG. 8, in order to obtain light emission in a relatively long wavelength range like green-red region, InGaN needs to be used as a material which comprises the light emitting layer 120. FIG. have. For this reason, conventionally, the light emitting layer 120 is composed of a single layer of InGaN, or as disclosed in Japanese Patent Laid-Open Publication No. Hei 10-270758, and using a InGaN well layer and a GaN barrier layer, multiple quantum crystals (MQW) Quantum Well) was used. As the light emission wavelength is increased, the In (indium) composition needs to be increased.

However, the lattice constant of InN is about 3.55 A, and when In composition is increased in InGaN, the "error" of the lattice constant with the sapphire substrate or the GaN layer becomes larger. As a result, in the conventional light emitting device, when the In composition of the light emitting layer 120 is increased, the lattice mismatch between the sapphire substrate 118 and the GaN layers 105 and 119 is caused due to the "lattice mismatching system" as described above. Becomes larger, resulting in a problem that the crystallinity of the light emitting layer 120 is extremely deteriorated.

In addition, since In has a high equilibrium vapor pressure, when the In composition of the light emitting layer 120 is increased, there is also a problem that, in the case of crystal growth, the light emitting layer once crystal grown is separated or re-evaporated.

As described above, in a gallium nitride compound semiconductor light emitting device having a structure as illustrated in FIG. 8, it is difficult to grow high-quality crystals as the light emission wavelength is increased, and thus there is a problem that the light emission power is greatly reduced. For this reason, in the conventional light emitting device, the upper limit of the In content of In _x Ga _1-x N constituting the light emitting layer 120 is at most x = 0.3, and in terms of wavelength, light emission from 450 nm blue to green is limited. It was.

In the conventional light emitting device, in order to make the wavelength longer, there is also a method of generating light emission through impurity levels by doping both Zn and Si, but the shortcoming of the emitted light is wider, resulting in poor monochromatic properties. However, there are drawbacks such as light emission power is smaller than band short emission.

In addition, if the GaN layer is grown on a sapphire substrate having a large "error" in the lattice constant as well as the initial characteristics, even when grown through the buffer layer, a large stress is applied to the crystal, resulting in many lattice defects, resulting in reliability of the light emitting device, That is, there also existed a problem that the long-term stability of a lifetime or each characteristic also fell. This problem is particularly serious for the realization of high performance semiconductor lasers.

Full color displays require red, blue and green light emission. However, since the above-mentioned various problems exist, it was extremely difficult to conventionally obtain a high luminance long wavelength region, that is, red light emission using a gallium nitride system material.

On the other hand, in the conventional light emitting device as illustrated in FIG. 8, since the sapphire used as the substrate 118 is not conductive, it is necessary to form both the p-side electrode and the n-side electrode above the light emitting device. Therefore, there is a problem that the required chip area is increased, the number of elements obtained from one wafer is small, and the cost is high.

On the other hand, in the conventional light emitting device as shown in FIG. 8, it is necessary to provide the insulating film 121 under the bonding pad 107 in order to cut off a current, and there also existed a problem that it was complicated from a structural viewpoint and a manufacturing process viewpoint.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and provides a semiconductor light emitting device that can reliably obtain long wavelength light emission from green to red region by reliably growing a light emitting layer having a higher In composition than deterioration of crystallinity. The purpose is to do that.

Another object of the present invention is to provide a semiconductor light emitting device and a method of manufacturing the same, which can reliably and easily form a current blocking structure.

1 is a cross-sectional view conceptually showing a semiconductor light emitting device according to the present invention;

2 is a graph showing the relationship between lattice constants in the a-axis direction of GaN, InN, and AlN;

3 is a conceptual diagram showing a state of lattice matching when epitaxially growing each layer of an MQW layer on a GaN substrate;

4 is a graph showing current-optical power characteristics of the light emitting device according to the first embodiment;

5 is a cross-sectional view conceptually illustrating a semiconductor light emitting device according to a second exemplary embodiment of the present invention;

6 is a cross-sectional view conceptually illustrating a semiconductor light emitting device according to a third embodiment of the present invention;

7 is a cross-sectional view conceptually illustrating a semiconductor light emitting device according to a fourth embodiment of the present invention;

8 is a schematic cross-sectional view showing a typical example of a conventional gallium nitride compound semiconductor light emitting device.

<Explanation of symbols for main parts of drawing>

10A ~ D --- semiconductor light emitting device, 11 --- substrate,

12 --- n-GaN buffer layer, 13 --- MQW light emitting layer,

13a --- InGaN layer, 13b --- AlGaN layer,

14 --- p-AlGaN cladding layer, 15 --- p-GaN layer,

16 --- transparent electrodes, 17 --- bonding pads,

18 --- protective film, 19 --- n-side electrode,

20 --- n-AlGaN cladding layer, 24 --- n-GaN guide layer,

25 --- p-AlGaN layer, 26 --- p-GaN guide layer,

27 --- insulating film (layer), 28 --- p-side electrode.

In the semiconductor light emitting device of the present invention for solving the above problems, a semiconductor light emitting device comprising a substrate and a light emitting layer provided on the main surface of the substrate, the light emitting layer is a gallium nitride compound having a larger lattice constant than the substrate A first layer made of a semiconductor and a second layer made of a gallium nitride compound semiconductor having a lattice constant smaller than that of the substrate, the first layer being substantially elastic in a direction parallel to the main surface by the second layer. Compressed to reduce the difference in lattice constant with the substrate.

Here, the first layer is made of In _x Ga _1-x N (0 ≦ x ≦ 1), and the second layer is Al _y Ga _z In _1-yz N (0 <y ≦ 1, 0 ≦ z ≦ 1, y + z ≤ 1).

In addition, the first layer has a layer thickness of about the wavelength of the electron de-broy wave.

In addition, the substrate is characterized in that consisting of a lattice matching material with GaN.

More specifically, the substrate is characterized in that made of GaN.

The light emitting layer is formed by alternately stacking a plurality of the first layers and a plurality of the second layers, and at least one of the plurality of first layers has a band gap different from that of the other first layers. .

The light emitting layer may be formed by alternately stacking a plurality of the first layers and a plurality of the second layers, and at least one of the plurality of first layers may include a first layer having a different compression amount received from an adjacent second layer. Is different, and emits light having a wavelength different from that of the other first layers.

Further, white light is obtained by synthesizing light emitted from each of the plurality of first layers.

In addition, the semiconductor light emitting device of the present invention includes a first conductive semiconductor and an electrode provided in contact with the first conductive semiconductor, wherein the contact portion between the semiconductor and the electrode has a low contact resistance. And a second region having a high contact resistance,

In the first region, a first metal capable of ohmic contact with the semiconductor of the first conductivity type contacts the semiconductor of the first conductivity type, and in the second region, the first metal and the second conductive A mixture with a second metal capable of ohmic contact with a semiconductor of a type is made in contact with the semiconductor of the first conductive type.

On the other hand, the method of manufacturing a semiconductor light emitting device of the present invention comprises the steps of depositing a first metal capable of ohmic contact with the semiconductor of the first conductivity type on the surface of the semiconductor of the first conductivity type, Depositing a second metal capable of ohmic contact with a second conductive semiconductor on a portion of the surface of the semiconductor; and reacting the first metal with the second metal to the semiconductor of the first conductive semiconductor. It is characterized by comprising a step of forming a region of high contact resistance.

Embodiment

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail, referring drawings.

According to the first embodiment of the present invention, the "error" of the lattice constant between the light emitting layer including the InGaN layer and the GaN layer can be alleviated. As a means for this, the InGaN layer of the light emitting layer is laminated with the AlGaN layer. InGaN has a lattice constant larger than GaN, while AlGaN has a lattice constant smaller than GaN. Therefore, the light emitting layer in which the InGaN layer and the AlGaN layer are laminated can be adjusted so that the average lattice constant becomes very close to GaN. At this time, if the thickness of the InGaN layer is made somewhat thin, i.e., less than or equal to the electron de- broy wave or the "critical film thickness", the compressive stress is applied to the InGaN layer without causing crystal defects, and the lattice constant is GaN. Can be close to.

This effect is extremely remarkable when the light emitting element adopts the configuration of "lattice matching system". In other words, by adopting a GaN substrate or a substrate capable of lattice matching with the GaN layer, the "error" of the lattice constant between the substrate and the growth layer is extremely small, and the crystal defects attracted to each growth layer containing the light emitting layer can be greatly reduced. have. In the present invention, the crystal defects attracted to the InGaN layer can be more remarkably reduced in such a "grid matching system".

As an example, the case where GaN is used as a substrate will be described. In this case, when the Al composition of the growth layer increases, the tensile stress acts on the interface direction, and the compressive stress acts on the direction perpendicular thereto. When the In composition increases, the compressive stress on the interface direction and the tensile stress on the direction perpendicular thereto. Works. The InGaN layer is subjected to compressive stress in the in-plane direction by the AlGaN layer, and the crystal lattice is elastically reduced to lattice match with the GaN layer. As a result, according to the present invention, the lattice constant of InGaN of the light emitting layer can be closer to GaN in the configuration of the "lattice matching system". As a result, even if the In composition of the light emitting layer is made high, crystal defects at the crystal layer or at the interface can be greatly reduced.

In addition, according to the present invention, by alternately growing the layer containing In of the thin film and the layer containing Al of the thin film, re-evaporation or decomposition of the InGaN crystal, which is a problem in the case of crystal growth, can be prevented, thereby making it possible to obtain high quality crystals. You can certainly get it. As a result, a light emitting layer having a higher In composition than the conventional one can be realized, and a light emitting device having a high luminance in green or a longer wavelength red region can be realized.

In the case where InGaN quantum crystal is a single layer, an equivalent effect can be obtained even if an AlGaN layer is introduced using the cladding layer as a barrier. When the light emitting layer has a multi-quantum crystal structure, all of the barrier layers may be made of AlGaN, or a combination of InGaN and AlGaN produces the same effect. In addition, in order to obtain light emission at a longer wavelength, when the In composition of the InGaN layer sandwiched by the AlGaN layer is increased from the substrate side to the surface, a good InGaN layer that does not deteriorate in crystallinity can be realized. In addition, when the growth layer is formed on a conductive substrate such as GaN, the electrode can be formed on the back surface of the substrate, so that the wafer area can be effectively used.

On the other hand, according to the second embodiment of the present invention, the so-called "current blocking structure" can be formed reliably and easily. For example, it is possible to reliably and easily realize a structure for preventing current from flowing under the bonding pad that shields the light emitted from the light emitting layer. That is, when a region containing the n-side electrode material is formed in a part of the formation region of the p-side electrode and subjected to annealing, these electrode metals react to form a region having a high contact resistance. When an overcoat electrode serving as a bonding pad is formed in this high resistance region, no current is injected into the light emitting layer and no light is emitted. In the formation of this structure, when the n-side electrode material is used for the overcoat electrode of the p-side electrode, the manufacturing process can be efficiently carried out. In portions other than this region, the p-side electrode is in contact with the semiconductor layer with sufficiently low contact resistance, and current is injected to the light emitting layer to emit light.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail, referring a specific example.

First embodiment

First, the first embodiment of the present invention will be described.

1 is a cross-sectional view conceptually illustrating a semiconductor light emitting device according to the present invention. That is, the light emitting device 10A includes an n-GaN buffer layer 12, an MQW layer 13 (light emitting layer), and a p- (p type) AlGaN cladding layer 14 on the n- (n type) GaN substrate 11. , p-GaN layer 15 has a structure in which the layers are sequentially stacked. Each crystal layer can be grown by methods such as MOCVD (Metal-Organic Chemical Vapor Deposition) or MBE (Molecular Beam Epitaxy).

The MQW layer 13 has a structure in which an InGaN layer well layer 13a and an AlGaN layer barrier layer 13b are alternately stacked as shown in the insertion enlarged view of FIG. Here, the layer thickness of the InGaN layer 13a is about 20 angstroms, and the layer thickness of the AlGaN layer 13b is about 10 angstroms.

2 is a graph showing the relationship between lattice constants in the a-axis direction of GaN, InN, and AlN.

3 is a conceptual diagram showing the state of the lattice constant when epitaxially growing each layer of the MQW layer on a GaN substrate. 3A shows the relationship between the lattice constants of the GaN substrate 11 and the InGaN layer 13a, and FIG. 3B shows the lattice constants of the GaN substrate 11 and the AlGaN layer 13b. Represents a relationship. As shown in these figures, the InGaN layer 13a has a larger lattice constant than the GaN substrate 11, and the AlGaN layer 13b has a smaller lattice constant than the GaN substrate 11. Therefore, when these layers are epitaxially grown on the GaN substrate 11 as it is, crystal defects occur in the crystal layer or the interface due to the "error" of the lattice constant.

On the other hand, as shown in Fig. 3C, when the thin film of InGaN layer 13a and AlGaN layer 13b are laminated, the compressive stress in the in-plane direction is applied to the InGaN layer 13a and in-plane to the AlGaN layer 13b. Direction tensile stress is applied respectively. The lattice constant of each layer can be adjusted very close to the GaN substrate 11. At this time, the InGaN layer 13a and the AlGaN layer 13b can be reliably suppressed from the occurrence of crystal defects if the thickness of each of the InGaN layer 13a and the AlGaN layer 13b is less than the so-called "critical film thickness", that is, the elastically deformable film thickness.

As a result, as shown in Fig. 3D, even when epitaxially grown on the GaN substrate 11, extremely good lattice matching can be realized.

In this way, after the layer 13a containing the high concentration of In is grown extremely thin, the AlGaN layer 13b of the thin film is directly stacked and capped to prevent decomposition or re-evaporation of the InGaN layer 13a. Higher concentrations are now possible.

The MQW layer 13, that is, the light emitting layer formed in this way can significantly suppress the occurrence of crystal defects even when the In composition of the InGaN layer 13a is set high. As a result, it is possible to obtain a light emitting device having a higher luminance and a longer life than a conventional wavelength region.

Referring back to FIG. 1, after the epitaxial growth of each crystal layer 12 to 15 on the GaN substrate 11, the Ni layer and the Au layer are deposited on the surface of the p-GaN layer 15 by vapor deposition. a transparent electrode 16 laminated with and further to form the protective film 18 by SiO ₂ film is deposited and patterned using a PEP (Photo Engraving process) method by thermal CVD. Further, a Ti layer, which is a material of the n-side electrode, is deposited as a p-side bonding pad 17 on the transparent electrode 16 exposed to the opening of the protective film 18, and further, an Au layer or the like is laminated. Patterning of the bonding pad 17 can be performed by the lift-off method using a resist, for example. After polishing the back surface of the GaN substrate 11, an n-side electrode 19 composed of a Ti layer and an Au layer is formed, and flash annealing is performed at 800 ° C. for about 20 minutes.

When the device is fabricated in this manner, in the case of flash annealing of the n-side electrode 19, the Ni / Au transparent electrode 16 and the Ti / Au bonding pad 17 cause an electrode reaction on the p-side, resulting in p-GaN. The contact resistance to the layer 15 becomes large. Therefore, the current hardly flows under the bonding pads 17, so that light emission does not occur. On the other hand, in the transparent electrodes 16 other than the bonding pads 17, since current spreads in-plane and flows through the p-GaN layer 15, uniform light emission is obtained. As a result, light emission from the bottom of the bonding pad 17, which is the light shielding body, can be effectively suppressed, so that the light extraction efficiency of light can be improved.

4 is a graph showing current-optical power characteristics of the light emitting device according to the present embodiment. Here, the In composition of the InGaN layer 13a of the light emitting layer 13 was 60%. In addition, in FIG. 4, the characteristic of the light emitting element of the conventional structure illustrated in FIG. 8 was also shown as a comparative example. The light emitting device of the present invention had a voltage of 3.5 V, a light output of 2.7 mW, and a light emission wavelength of 550 nm at a current value of 20 mA. Compared with the conventional example, the optical power at an injection current of 20 mA was about three times.

Moreover, in this embodiment, a part of the p-side electrode is set as a high resistance region, but the above-described manufacturing method is not limited to the p-side electrode, and the same application is also possible for the n-side electrode. As a result, when the p-side electrode material is laminated to a part of the formation region of the n-side electrode and heat-treated to an appropriate level, the n-side electrode material and the p-side electrode material are alloyed to form a high resistance region on the n side of the light emitting device. can do.

In addition, the present invention can be similarly applied to the case where both the p-side electrode and the n-side electrode are formed on the surface side of the substrate as in the conventional example illustrated in FIG. 8. In this case, if the materials of the overcoat electrode such as Au and the n-side electrode are made the same, the process is performed efficiently.

In the present embodiment, an example in which the light emitting layer 13 is composed of an MQW structure including an InGaN well layer 13a and an AlGaN barrier layer 13b has been described. In this configuration, the composition of In and Al of each layer is It is not necessarily the same. In other words, when the amount of distortion or the In composition of the InGaN well layer 13a is changed, light emission of various wavelengths can be obtained.

Second embodiment

Next, a second embodiment of the present invention will be described.

5 is a cross-sectional view conceptually illustrating a semiconductor light emitting device according to a second exemplary embodiment of the present invention. In FIG. 1, the same code | symbol is attached | subjected to the part same as the above-mentioned part in FIG. 1, and detailed description is abbreviate | omitted. In the light emitting element 10B according to the present embodiment, an n-AlGaN cladding layer 20 is provided. Further, the well layer 13a constituting the light emitting layer is one layer, and AlGaN layers 13b and 13b are provided for applying distortion to both or one side thereof. Moreover, in FIG. 5, the case where AlGaN layer 13b is provided in the both sides of the well layer 13a was illustrated.

These layers 13a and 13b may be doped with impurities or undoped, respectively. In such a structure, the Al composition and the InGaN light emitting layer of the n-AlGaN cladding layer 20, the p-AlGaN cladding layer 14, and the AlGaN layers 13b and 13b for applying distortion to the InGaN light emitting layer 13a. The amount of distortion applied depends on the relationship with the In composition of (13a). In this way, the amount of distortion applied more precisely can be controlled. In addition, the AlGaN layer tends to be cracked when thick, but according to this embodiment, there is an advantage that the total thickness can be made thin.

Furthermore, in Fig. 5, only one layer of AlGaN distortion layers 13b and 13b are provided on the p side and the n side of the InGaN layer 13a, respectively, but these AlGaN layers each consist of a plurality of layers having different Al compositions. You may use it.

Third embodiment

Next, a third embodiment of the present invention will be described.

6 is a cross-sectional view conceptually illustrating a semiconductor light emitting device according to a third exemplary embodiment of the present invention. In FIG. 1, FIG. 5, the same code | symbol is attached | subjected to the part same as the above-mentioned part in FIG. 1, FIG. 5, and detailed description is abbreviate | omitted. In the light emitting element 10C according to the present embodiment, the well layer 13a has three layers, and the emission wavelength is changed by changing the respective In compositions, so that red, green, and blue light emission of 640, 540, and 460 nm are respectively performed from the surface side. To produce white light. Since bright light emission is hardly obtained on the long wavelength side, it is the structure which makes it emit light from the surface side more.

However, on the contrary, the well layer on the long wavelength side, that is, the well layer having a high In composition may be provided on the side close to the substrate 11. That is, three well layers are arranged so that the band gap increases in order from the substrate side. In this way, the situation that light emission from the well layer on the substrate side is absorbed by the upper well layer can be prevented.

In addition, the white light can be realized by combining the light emitted from each well with the light that has undergone color conversion (for example, red which is difficult to obtain bright light) by bringing the ultraviolet light emitted from the light emitting element into the phosphor. As an example, when the In composition of the well layer in this case is set to In = 0.02, 0.3, and 0.5 from the surface, the emission wavelengths are 370, 460, and 540 nm, respectively. Among them, white light can be obtained by converting ultraviolet light of 370 nm into red light by touching the phosphor and converting blue and green light from each well.

Fourth embodiment

Next, a fourth embodiment of the present invention will be described.

7 is a cross-sectional view conceptually illustrating a semiconductor light emitting device according to a fourth exemplary embodiment of the present invention. In FIG. 1, FIG. 5, FIG. 6, the same code | symbol is attached | subjected to the part same as the above-mentioned part in FIG. 1, FIG. 6, and detailed description is abbreviate | omitted. The light emitting element 10D according to the present embodiment is a semiconductor laser. That is, on the n-AlGaN cladding layer 20, an n-GaN guide layer 24, an MQW light emitting layer 13, a p-AlGaN layer 25, and a p-GaN guide layer 26 are provided in this order. The p-AlGaN cladding layer 14 and the p-GaN layer 15 are laminated thereon.

The light emitting layer 13 can have, for example, an MQW type structure as shown in FIG. In this case, the In composition of the InGaN layer 13a may be 0.2, and the Al composition of the AlGaN layer 13b may be 0.02.

In addition, on the p-GaN layer 15, an insulating film 27 provided with a stripe-shaped opening is provided on the p-GaN layer 15, and a p-side electrode 28 is provided thereon.

According to this embodiment, it is possible to stably obtain laser light with a longer wavelength and a higher power than before.

Further, instead of the insulating film 27, as described in the first embodiment, an n-side electrode material may be provided. In other words, an n-side electrode material having a stripe-shaped opening is formed on the p-GaN layer 15, and the p-side electrode is laminated on the entire surface of the p-GaN layer 15 to perform heat treatment, thereby increasing the resistance of the region outside the stripe. It is possible.

In the above, embodiment of this invention was described, referring a specific Example. However, the present invention is not limited to these examples.

For example, the board | substrate used by this invention is not limited to GaN, In addition, if it is a material with small lattice mismatch with GaN, the same effect can be acquired. For example, when MnO, NdGaO ₃ , ZnO, LiAlO ₂ , LiGaO _2, or the like is used as the substrate material, lattice mismatch with the GaN layer can be suppressed to within about 2%. Therefore, by using the substrate made of these materials, the lattice match with the GaN layer is good, and the effect of the present invention can be remarkably obtained.

In addition, the method for forming an electrode described above as a second embodiment of the present invention is not limited to a gallium nitride-based semiconductor light emitting device, and can be similarly applied to a semiconductor light emitting device made of all other materials to obtain the same effect. Can be. For example, the same can be applied to semiconductor light emitting devices made of various semiconductors such as GaP, GaAsP, AlGaInP, GaAlP, InP, InGaAs, InGaAsP and the like.

As described above, according to the present invention, by using a light emitting layer in which a semiconductor layer having a large lattice constant and a semiconductor layer having a small lattice constant are stacked on a substrate, the "error" of the lattice constant between the substrate and the light emitting layer is alleviated. You can. At this time, if the film thickness of each layer is less than or equal to the wavelength of the electron de broy wave or the "critical film thickness", compressive stress is applied to each layer without generating crystal defects, and the lattice constant is applied to the substrate. You can close it.

This effect of the present invention becomes extremely remarkable when the light emitting element adopts the configuration of "lattice matching system". That is, in the gallium nitride system, by employing a GaN substrate or a substrate capable of lattice matching with a GaN layer, the light emitting layer can be made extremely small in comparison with the conventional sapphire substrate by using the "error" of the lattice constant between the substrate and the growth layer. Crystal defects attracted to each growth layer contained can be greatly reduced. In the present invention, the crystal defects attracted to the InGaN layer can be more remarkably reduced in such a "grid matching system". Therefore, the effect which "lattice matching system" has can be made more remarkable.

As a result, even if the In composition of the light emitting layer is increased, crystal defects at the crystal layer or at the interface can be greatly reduced.

In addition, according to the present invention, by alternately growing the In-containing layer of the thin film and the Al-containing layer of the thin film, re-evaporation or decomposition of the InGaN crystal, which is a problem in the case of crystal growth, can be prevented, thereby making it possible to obtain high quality crystals. You can certainly get it. As a result, a light emitting layer having a higher In composition than the conventional one can be realized, and a light emitting device having a high luminance in green or a longer wavelength red region can be realized.

In addition, in order to obtain light emission at a longer wavelength, when the In composition of the InGaN layer sandwiched by the AlGaN layer is increased from the substrate side to the surface, a good InGaN layer that does not deteriorate in crystallinity can be realized. In particular, when the In composition of each well layer is changed to emit red, blue, and green light, white light emission is obtained as a result. It is experimentally known to control the wavelength to some extent by controlling the amount of distortion for each well layer. By controlling the In composition and the lattice distortion, red, blue, and green light can be emitted, resulting in white light emission.

In addition, according to the present invention, when the growth layer is formed on a conductive substrate such as GaN, an electrode can be formed on the back surface of the substrate, so that the effect that the wafer area can be effectively used is also obtained.

On the other hand, according to the second embodiment of the present invention, the so-called "current blocking structure" can be formed reliably and easily. This effect of the present invention is not limited to a light emitting element using a gallium nitride compound semiconductor, and can be similarly applied to a light emitting element using all other materials.

As described above, according to the present invention, it is possible to provide a semiconductor light emitting element which can reliably obtain long wavelength light emission from green to red region, and can reliably and easily form a current blocking structure, and a manufacturing method thereof. There are so many industrial advantages.

Claims (10)

Substrate, In the semiconductor light emitting device having a light emitting layer provided on the main surface of the substrate, The light emitting layer, A first layer made of a gallium nitride compound semiconductor having a larger lattice constant than the substrate; A second layer made of a gallium nitride compound semiconductor having a lattice constant smaller than that of the substrate, And the first layer is elastically compressed in a direction parallel to the main surface by the second layer, so that a difference in lattice constant from the substrate is reduced. The method of claim 1, wherein the first layer is formed of In _x Ga _1-x N (0 ≦ x ≦ 1). The second layer is a semiconductor light emitting device, characterized in that the Al _y Ga _z In _1-yz N (0 <y ≤ 1, 0 ≤ z ≤ 1, y + z ≤ 1). The semiconductor light emitting device according to claim 1 or 2, wherein the first layer has a layer thickness of about the wavelength of the electron de-broy wave. The semiconductor light emitting device according to any one of claims 1 to 3, wherein the substrate is made of a material that lattice matches with GaN. The semiconductor light emitting device according to any one of claims 1 to 4, wherein the substrate is made of GaN. 6. The light emitting layer of claim 1, wherein the light emitting layer is formed by alternately stacking a plurality of the first layers and a plurality of the second layers. At least one of the plurality of first layers has a band gap different from that of the other first layers. 6. The light emitting layer of claim 1, wherein the light emitting layer is formed by alternately stacking a plurality of the first layers and a plurality of the second layers. At least one of the plurality of first layers is different from the first layer in which the amount of compression received from the adjacent second layer is different, thereby emitting light having a wavelength different from that of the other first layer. The semiconductor light emitting device according to claim 6 or 7, wherein white light is obtained by synthesizing light emitted from each of the plurality of first layers. A semiconductor of the first conductivity type, An electrode provided in contact with the semiconductor of the first conductivity type, The contact portion between the semiconductor and the electrode includes a first region having a low contact resistance and a second region having a high contact resistance, In the first region, a first metal capable of ohmic contact with the semiconductor of the first conductivity type contacts the semiconductor of the first conductivity type, In the second region, a semiconductor light emitting element comprising a mixture of the first metal and a second metal capable of ohmic contact with a second conductive semiconductor in contact with the first conductive semiconductor. . Depositing a first metal capable of ohmic contact with the first conductive semiconductor on a surface of the first conductive semiconductor; Depositing a second metal capable of ohmic contact with a portion of the surface of the semiconductor of the first conductivity type with respect to the semiconductor of the second conductivity type, and And forming a region having a high contact resistance with respect to the first conductive semiconductor by reacting the first metal and the second metal.